hythamfekry

HI ,
i moved Ultegra R8050 groupset to a different frame , went through the steps in Ultegra manual , only problem is on big ring/smallest sprocket ..
it gives like a wiggle sound "rather than friction or rub" , which i can feel when rotating crank by hand ..
i've tried adjusting b-tension screw , it didn't help , high limit of RD is not the problem either ..
Note : chain is same length as it was on old frame as both frames have same chainstay , i did the sizing as per Shimano manual method "add 1 to 3 links when chain on big ring/big sprocket"
Any Ideas ?

Steve B.

My only thought is that Di2 is known for not liking big ring, small cog combo, 2nd smallest cog is an issue as well. My system locks those out unless I cheat and set it up as a crank and/or cassette that I’m not really using - 53/39 crank I think it likes. So maybe the R derailer is wanting to shift the chain to a larger cog.

These are E-Tube settings, did you change anything during the swap ?

hythamfekry

what's locked "as a default setting" is small ring/ smallest two sprockets .. my setup is 53-39 with 12-25 cassette .. E-tube is configured the same .. how do you configure yours ?
same group "with crank and cassette" was working fine on the previous frame ,

jadocs

I've never heard of Di2 not liking big ring small cog.

OP please clarify what you mean by "wiggle sound" otherwise you are going to be subjected to everyone's assumptions of what you mean.

For example, based on your description, my assumption is you are "feeling" the chain sticking slightly to your upper jockey wheel, which in fact is an alignment problem.

hythamfekry

I already adjusted index and limits as well as , chain is not rubbing or bouncing on sprocket ...
when rotating crank by hand on high RPM , i sense like a vibration , sound is more like something is drivetrain i wiggling/vibrating , rather that the sound of friction/rub when indexing is not adjusted ..
that's only on big ring / smallest sprocket "12 teeth" , it's less on the 2nd smallest sprocket "13 teeth" and not noticed on larger sprockets

jadocs

What you are feeling is the chain rotating around the small cog. That buzz I think you are referring to gets quieter as you shift up as you described.

Steve B.

Possibly they changed the E-Tube software, but when I set up my system 2 yrs. ago, trying to use a 34/50 crank and about any cogset, 11-23, 12-25, the system would not allow a shift to big ring/small or next cogs. This was with Synchro turned off. You could cheat and set it up with certain crank/cassette combos. I know telling E-tube I had a 39/53 crank allowed those shift combos with a 12-25.

jadocs

Yeah that's weird, I told E-Tube I had a 50/34 and 11-30, and no issues on my end.

hythamfekry

chain legnth was my first suspect , however chain is already 106 link , chain stay is 40.5 cm , i tried Shimano method "placing chain on big ring/big sprocket + 1 to 3 links
also tried this equation below , in both methods chain length shouldn't be shorter
"chain stay legnth by inch *2 + cranks teeth count/4 + largest sprocket count/4" + 1 ===> gives number of full links
using b-tension to tighten chain a little didn't help also ..

Regarding E-tube , i already have 53-39 crank .. so possible nothing i can do there

jadocs

Your chain is fine. Think of it this way, your chain is made up of links, when they rotate around a small cog it is going to be noisier than rotating around a larger cog because of the chain angle. It is more extreme on the small cog, when you shift to larger cog, the angle is much more relaxed, hence less noise.

Now what you need to do is be able to identify noises associated with other things such as poor indexing which causes noise from the chain rubbing against the cogs, etc... If all that checks out, then what I think you are hearing is what I described above. Also make sure you are using good chain lube and your chain is lubed properly. A poorly lubed chain will be noisier than one that is properly lubed.

TerryDi2C

They lock out small ring, smallest sprockets on r8050 / r9150 and newer, depending on the chain rings / cassette you have set up.
You can "cheat" this using the method you described, or you could disable 'gear position control' in the e-tube software.